(1) Field of the Invention
This invention relates to the determination of the endpoint in chemical mechanical polishing, CMP, and more specifically to integrating a current which is proportional to the rate of removal of the film being polished and stopping the polishing when a pre-determined amount of the film has been removed.
(2) Description of the Related Art
As the use of chemical mechanical polishing becomes more widely used in integrated circuit manufacture it becomes increasingly important to find improved methods for determination of the endpoint of the polishing.
U.S. Pat. No. 5,492,594 to Burke et al. describes a tool which uses a plurality of electrodes in an electrolyte bath to determine the thickness of dielectric remaining on the surface of the wafer being polished.
The invention of this Patent Application generates the integral over time of a current proportional to the rate of removal of a dielectric layer being polished. In this way the amount of dielectric layer removed is determined. The endpoint is reached when a predetermined amount of the dielectric layer has been removed.